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US4240022A - Battery charging circuit for portable power tool - Google Patents

Battery charging circuit for portable power tool Download PDF

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Publication number
US4240022A
US4240022A US05/891,305 US89130578A US4240022A US 4240022 A US4240022 A US 4240022A US 89130578 A US89130578 A US 89130578A US 4240022 A US4240022 A US 4240022A
Authority
US
United States
Prior art keywords
cells
circuit
capacitor
current source
charging
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US05/891,305
Other languages
English (en)
Inventor
David C. Kilinskis
Louis J. Vassos
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch Tool Corp
Original Assignee
Skil Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Skil Corp filed Critical Skil Corp
Priority to US05/891,305 priority Critical patent/US4240022A/en
Priority to NL7901821A priority patent/NL7901821A/xx
Priority to GB7908751A priority patent/GB2018061B/en
Priority to AU45131/79A priority patent/AU521571B2/en
Priority to CA323,826A priority patent/CA1128989A/en
Priority to IT48464/79A priority patent/IT1115071B/it
Priority to JP3539879A priority patent/JPS54139033A/ja
Priority to SE7902748A priority patent/SE432328B/sv
Priority to BE0/194276A priority patent/BE875165A/xx
Priority to DE19792912509 priority patent/DE2912509A1/de
Application granted granted Critical
Publication of US4240022A publication Critical patent/US4240022A/en
Assigned to S-B POWER TOOL COMPANY reassignment S-B POWER TOOL COMPANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SKIL CORPORATION
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H02J7/977—
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S320/00—Electricity: battery or capacitor charging or discharging
    • Y10S320/18—Indicator or display
    • Y10S320/21—State of charge of battery
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S320/00—Electricity: battery or capacitor charging or discharging
    • Y10S320/22—Line impedance, e.g. resistor

Definitions

  • This invention relates to battery charging circuits and, in particular, to circuits suitable for use with power tools which include a self-contained battery pack.
  • power tools which include a self-contained battery pack.
  • the batteries used for such application are of the nickel cadmium type and are suitable for recharging at a split rate. That is, the battery can be recharged at a fast rate as long as this charge rate is discontinued when the full charge condition is reached. Thereafter, only a trickle charge may be applied if damage to the battery is to be avoided. The trickle charge will maintain the battery in a full charge condition for an indefinite period of time. Failure to properly switch from fast charge to trickle charge will quickly cause damage to the battery cells requiring their replacement.
  • Another object of the invention is to provide a battery charging circuit capable of recharging a battery in a fast charge mode and maintaining it at full charge by applying a trickle charge thereafter.
  • FIG. 1 is a battery charging circuit according to a first embodiment of the invention.
  • FIG. 2 is a battery charging circuit according to a second embodiment of the invention.
  • FIG. 3 is a circuit according to a third embodiment of the invention.
  • FIG. 4 is a waveform diagram useful in understanding the operation of the invention.
  • the circuit may be conveniently broken up into three sections for ease of discussion. These sections include a current source 10, a trickle charge section 12 and a fast charge section 14.
  • the circuit is adapted to apply charging current to battery cells indicated schematically at 16.
  • These cells are of the nickel-cadmium type which may be charged at a split rate. That is, they may be fast charged until they approach a full charge condition and then trickle charged thereafter for an indefinite period.
  • a characteristic of such cells is that when they approach full charge there is a significant temperature rise. If fast charge is not promptly terminated after the temperature rise occurs the cells will be quickly damaged. Thus, the temperature rise in the cells is a signal which may be utilized to switch to a trickle charge current.
  • the circuit of FIG. 1 provides two paths or circuits from the current source 10 to the cells 16.
  • the first path is through the trickle charge section 12.
  • the second path is through the fast charge section 14 and a thermostat 18.
  • the thermostat 18 is operatively connected to detect a temperature rise in the cells 16 when they approach the full charge condition.
  • Thermostat 18 will close upon the cells cooling and, in the absence of the present invention, fast charging would resume.
  • Such a cyclical operation of the fast charge section is undesirable as it repetitively overcharges the cells to produce a temperature rise. This is avoided by the present invention.
  • the current source utilized to charge the battery cells produces a full waved rectified voltage, Vc, illustrated as waveform 20 in FIG. 4.
  • the current source includes a transformer T1 and a pair of diodes D1 and D2.
  • AC line voltage is connected to the primary of transformer T1 while the diodes D1 and D2 are connected to the secondary to produce the full wave rectified voltage, Vc, at terminal 22.
  • the secondary of transformer T1 is center tapped and connected to the negative terminal of the battery cells 16 via line 24.
  • the frequency of the voltage is 60 Hz.
  • the voltage waveform has a zero value every 8.3 msecs.
  • the rectified voltage is applied from terminal 22 to both the trickle charge section 12 and the fast charge section 14.
  • the trickle charge section includes a resistor R1 which limits the current to the battery cells 16 to a safe value which can be constantly applied without damage.
  • the trickle charge section 12 supplies the trickle current through the resistor R1 to positive terminal 26 of the battery.
  • resistor R1 Connected in parallel with resistor R1 is a light emitting diode D3 and its associated biasing resistor R2. When illuminated, diode D3 advises the user that the cells 16 are in trickle charge and thus the battery cells are substantially fully charged and ready for use.
  • a silicon controlled rectifier 28 having the usual anode, cathode and gate electrodes.
  • the anode of the SCR is connected to terminal 22 while the cathode is connected through the thermostat 18 to the positive terminal 26 of the cells.
  • the gate electrode of the SCR is connected to a junction 30 via resistor R3.
  • Connected between junction 30 and line 24 is a capacitor C1 and in parallel therewith a resistor R4. Switch S1 and diode D4 connect terminal 22 to junction 30.
  • the SCR 28 when the SCR 28 conducts it provides a direct charging path from the current source 10 to the battery cells 16. That path is interrupted when the thermostat 18 opens as the cells approach the full charge condition.
  • the elements connected to junction 30 serve to control the operation of the SCR until the thermostat 18 opens and to prevent operation of the SCR after the thermostat 18 opens.
  • the battery cells 16 When it is desired to initiate operation of the charging circuit the battery cells 16 are placed in the circuit and switch S1 is momentarily depressed. This applies the voltage Vc illustrated in FIG. 3 to junction 30.
  • Capacitor C1 rapidly charges up to and is clamped at approximately the maximum value of Vc by the diode D4.
  • the voltage Vc is also applied to the anode of the SCR while the battery voltage, Vb, is present at the cathode of the SCR. Since the battery is initially discharged, Vb will be much less than the maximum value of Vc.
  • the capacitor C1 When the instantaneous value of Vc applied to the anode of the SCR exceeds the battery voltage Vb on the cathode, the capacitor C1 will discharge through resistor R3 producing a current flow into the SCR gate electrode.
  • the fast charge cycling process repeats every 8.3 milliseconds (for 60 Hz operation) until the battery cells near full charge. As full charge is approached, the battery cells heat up and cause the thermostat 18 to open breaking the charging path through the fast charge section.
  • the thermostat will close when the cells cool off. It is desirable, however, to prevent the resumption of the fast charging and, accordingly, means are provided to disable the SCR gate circuit during the period that the thermostat is open.
  • Bleed resistor R4 is connected between terminal 30 and line 24 and permits C1 to discharge therethrough during the time period the thermostat is open.
  • the value of capacitor C1 and resistor R4 are selected to produce an RC time constant which is significantly greater than the 8.3 millisecond operating cycle.
  • the RC time constant of capacitor C1 and resistor R4 may be on the order of 100 times greater than the period of the voltage waveform (8.3 milliseconds).
  • Waveform 32 in FIG. 3 illustrates the voltage seen at terminal 26 during fast charging of the battery.
  • the battery voltage is at value Vb.
  • the SCR turns on, as at point 34, the voltage at terminal 26 increases in proportion to the voltage Vc thereby charging the battery until point 36 when the SCR shuts off.
  • FIG. 2 a second embodiment of the invention is illustrated.
  • the circuit includes a current source 10, a trickle charging section 12, and a fast charge section 14.
  • the difference between the FIG. 1 and FIG. 2 embodiment resides in the fast charge section 14.
  • junction 30 is connected to the current source through resistor R1 and diode D4.
  • the second embodiment initiates fast charge as soon as the battery cells 16 are placed in the charging circuit.
  • capacitor C1 Prior to placement of the cells 16 into the charging circuit, capacitor C1 is charged up through resistor R1 and diode D4 to a voltage approximating the maximum open circuit voltage Vco of the transformer T1.
  • Vco maximum open circuit voltage
  • diode D4 When the battery is placed in circuit with the charger the voltage on the anode of diode D4 drops to approximately Vb. This reverse biases diode D4 since the anode of the diode will be at a lower voltage than the cathode which is connected to capacitor C1. As a result diode D4 is effectively removed from the circuit during the fast charge cycle.
  • the trickle charge section applies a trickle charge to the cells and the LED is illuminated to indicate the full charge condition.
  • the circuit includes a current source 10, a trickle charge section 12 and a fast charge section 14.
  • the charging current path in the third embodiment does not include the thermostat 18.
  • the charging current path is directly from the current source through the fast charge section to the battery cell.
  • the thermostat 18 is connected between junction 40 and the negative terminal of the battery 42 while the cathode of the SCR 28 is connected directly to the positive terminal of the battery 16.
  • the thermostat when the thermostat operates it interrupts current flow to the gate circuit of the SCR rather than breaking the circuit from the current source to the positive terminal of the battery cell as in the first embodiment.
  • the result is identical, as will be described, but the thermostat switches substantially less current than in the first embodiment.
  • a potential problem with the first embodiment is premature opening of the thermostat due to self heating.
  • the current through the thermostat is usually on the order of 2 amps.
  • the current through the thermostat is on the order of a few milliamps.
  • the possibility of premature opening due to self heating is substantially eliminated. It will be obvious to those skilled in the art that a similar modification to the FIG. 2 embodiment can be made to remove the thermostat from the charging path if desired.
  • the FIG. 3 embodiment begins the charge cycle when the switch S1 is momentarily closed charging capacitor C1 to a voltage exceeding the threshold voltage for the SCR 28.
  • the battery cell 16 receives current through the fast charge section 14 from the current source 10. As the battery cells approach full charge the thermostat detects the heat therefrom and opens, thus disconnecting the gate portion of the fast charge circuit. The SCR will then turn off because the capacitor C1 will not be able to supply current through resistor R3 to turn the SCR back on due to the open circuit. Bleed resistor R4 will discharge the capacitor C1 while the thermostat is open to prevent reactivation of the SCR when the thermostat 18 closes.
  • resistor R4 and capacitor C1 are selected to produce an RC time constant which is an order of magnitude greater than the 8.3 millisecond operating cycle of the 60 hertz voltage.
  • the advantages of the charging circuits according to the present invention include the ability to safely and efficiently charge battery cells while utilizing a minimum number of components.
  • the circuit is simple and low in cost and does not require any manipulation by the user except the insertion of the battery cells into the circuit. Proper switching between the fast charge and trickle charge sections is insured by virtue of preventing the capacitor C1 from charging up sufficiently to initiate operation of the SCR until the battery cells are removed from the circuit.
  • the first and third embodiments are simple, low cost and provide for direct user control of the charging cycle.

Landscapes

  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Secondary Cells (AREA)
US05/891,305 1978-03-29 1978-03-29 Battery charging circuit for portable power tool Expired - Lifetime US4240022A (en)

Priority Applications (10)

Application Number Priority Date Filing Date Title
US05/891,305 US4240022A (en) 1978-03-29 1978-03-29 Battery charging circuit for portable power tool
NL7901821A NL7901821A (nl) 1978-03-29 1979-03-07 Schakeling voor het laden van een batterij voor een draagbaar gereedschap.
GB7908751A GB2018061B (en) 1978-03-29 1979-03-13 Battery charging circuit
AU45131/79A AU521571B2 (en) 1978-03-29 1979-03-15 Battery charging circuit for portable power tool
CA323,826A CA1128989A (en) 1978-03-29 1979-03-20 Battery charging circuit for portable power tool
IT48464/79A IT1115071B (it) 1978-03-29 1979-03-23 Circuito caricatore di batteria per utensile motorizzato portatile
JP3539879A JPS54139033A (en) 1978-03-29 1979-03-26 Battery*cell charging circuit
SE7902748A SE432328B (sv) 1978-03-29 1979-03-27 Krets for aterladdning av battericeller
BE0/194276A BE875165A (fr) 1978-03-29 1979-03-28 Circuit de charge de batteries pour outil a moteur portable
DE19792912509 DE2912509A1 (de) 1978-03-29 1979-03-29 Batterieladeschaltung

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US05/891,305 US4240022A (en) 1978-03-29 1978-03-29 Battery charging circuit for portable power tool

Publications (1)

Publication Number Publication Date
US4240022A true US4240022A (en) 1980-12-16

Family

ID=25397941

Family Applications (1)

Application Number Title Priority Date Filing Date
US05/891,305 Expired - Lifetime US4240022A (en) 1978-03-29 1978-03-29 Battery charging circuit for portable power tool

Country Status (10)

Country Link
US (1) US4240022A (it)
JP (1) JPS54139033A (it)
AU (1) AU521571B2 (it)
BE (1) BE875165A (it)
CA (1) CA1128989A (it)
DE (1) DE2912509A1 (it)
GB (1) GB2018061B (it)
IT (1) IT1115071B (it)
NL (1) NL7901821A (it)
SE (1) SE432328B (it)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4346336A (en) * 1980-11-17 1982-08-24 Frezzolini Electronics, Inc. Battery control system
US4370606A (en) * 1979-10-13 1983-01-25 Matsushita Electric Works, Ltd. Charging apparatus
US4394612A (en) * 1982-01-04 1983-07-19 Skil Corporation Battery charging circuit
US4447785A (en) * 1982-03-30 1984-05-08 Wright Bruce R Battery charger assembly
DE3311024A1 (de) * 1983-03-25 1984-10-04 Hitachi Koki Co., Ltd., Tokio/Tokyo Batterieladegeraet
US4528492A (en) * 1983-04-05 1985-07-09 Hitachi Koki Company, Limited Battery charger
US4623832A (en) 1982-11-12 1986-11-18 Ryobi Ltd. Secondary battery quick-charging circuit
US4649333A (en) * 1985-04-30 1987-03-10 Levitt-Safety Limited Two terminal nicad battery charger with battery voltage and temperature sensing
US4686444A (en) * 1984-11-21 1987-08-11 Samsung Electronics Co., Ltd. Battery charging circuit
US4712055A (en) * 1987-04-01 1987-12-08 The Singer Company Battery charger circuit
US4890004A (en) * 1988-11-21 1989-12-26 Beckerman Howard L Emergency light control and battery charging system
US5013993A (en) * 1987-09-04 1991-05-07 Black & Decker Inc. Thermally responsive battery charger
US5225763A (en) * 1991-03-20 1993-07-06 Sherwood Medical Company Battery charging circuit and method for an ambulatory feeding pump
US5245268A (en) * 1992-04-15 1993-09-14 Jason Wang Battery charger with current stabilizer
US5247238A (en) * 1991-04-05 1993-09-21 Yang Tai Her Battery charger automatic cut-off circuit
US5708350A (en) * 1996-08-09 1998-01-13 Eveready Battery Company, Inc. Recharging method and temperature-responsive overcharge protection circuit for a rechargeable battery pack having two terminals
US6243276B1 (en) 1999-05-07 2001-06-05 S-B Power Tool Company Power supply system for battery operated devices

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6116764Y2 (it) * 1980-07-30 1986-05-23
FR2562723B1 (fr) * 1984-04-06 1986-08-22 Black & Decker Inc Dispositif perfectionne pour la mise en charge d'un ensemble accumulateur electrique

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3465230A (en) * 1967-01-09 1969-09-02 Mallory & Co Inc P R Thermal responsive recharge protection device to provide two level charging
US3518524A (en) * 1967-01-03 1970-06-30 Sunbeam Corp Cordless electric appliance
US3599072A (en) * 1969-10-06 1971-08-10 Richard B Becker Battery charger regulator circuit for periodically supplying charging current to a battery
GB1285069A (en) 1968-10-15 1972-08-09 Accumulateurs Fixes Battery charging arrangements
GB1316169A (en) 1970-12-29 1973-05-09 Singer Co Battery charging system
US3748568A (en) * 1971-04-28 1973-07-24 Bosch Gmbh Robert Automatically terminating battery charging arrangement with means for decreasing ripple effect
GB1335087A (en) 1970-12-02 1973-10-24 Motorola Inc Automatic battery charging circuit
US3911351A (en) * 1974-04-08 1975-10-07 Espey Mfg & Electronics Corp Battery charging protective circuit for use in charging nickel cadmium batteries
US3917990A (en) * 1974-04-11 1975-11-04 Gen Electric Battery charging control using temperature differential circuit
US3919618A (en) * 1974-06-10 1975-11-11 Gates Rubber Co Hysteresis battery charger
US3928792A (en) * 1975-02-24 1975-12-23 Gen Electric Method of resetting thermostat used with temperature controlled charging
US3935525A (en) * 1974-09-30 1976-01-27 The Black And Decker Manufacturing Company Battery charging circuit with thermostat control
GB1430322A (en) 1973-03-21 1976-03-31 Ceag Licht & Strom Emergency power supply

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3518524A (en) * 1967-01-03 1970-06-30 Sunbeam Corp Cordless electric appliance
US3465230A (en) * 1967-01-09 1969-09-02 Mallory & Co Inc P R Thermal responsive recharge protection device to provide two level charging
GB1285069A (en) 1968-10-15 1972-08-09 Accumulateurs Fixes Battery charging arrangements
US3599072A (en) * 1969-10-06 1971-08-10 Richard B Becker Battery charger regulator circuit for periodically supplying charging current to a battery
GB1335087A (en) 1970-12-02 1973-10-24 Motorola Inc Automatic battery charging circuit
GB1316169A (en) 1970-12-29 1973-05-09 Singer Co Battery charging system
US3748568A (en) * 1971-04-28 1973-07-24 Bosch Gmbh Robert Automatically terminating battery charging arrangement with means for decreasing ripple effect
GB1430322A (en) 1973-03-21 1976-03-31 Ceag Licht & Strom Emergency power supply
US3911351A (en) * 1974-04-08 1975-10-07 Espey Mfg & Electronics Corp Battery charging protective circuit for use in charging nickel cadmium batteries
US3917990A (en) * 1974-04-11 1975-11-04 Gen Electric Battery charging control using temperature differential circuit
US3919618A (en) * 1974-06-10 1975-11-11 Gates Rubber Co Hysteresis battery charger
US3935525A (en) * 1974-09-30 1976-01-27 The Black And Decker Manufacturing Company Battery charging circuit with thermostat control
US3928792A (en) * 1975-02-24 1975-12-23 Gen Electric Method of resetting thermostat used with temperature controlled charging

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4370606A (en) * 1979-10-13 1983-01-25 Matsushita Electric Works, Ltd. Charging apparatus
US4346336A (en) * 1980-11-17 1982-08-24 Frezzolini Electronics, Inc. Battery control system
US4394612A (en) * 1982-01-04 1983-07-19 Skil Corporation Battery charging circuit
US4447785A (en) * 1982-03-30 1984-05-08 Wright Bruce R Battery charger assembly
US4623832A (en) 1982-11-12 1986-11-18 Ryobi Ltd. Secondary battery quick-charging circuit
DE3311024A1 (de) * 1983-03-25 1984-10-04 Hitachi Koki Co., Ltd., Tokio/Tokyo Batterieladegeraet
US4528492A (en) * 1983-04-05 1985-07-09 Hitachi Koki Company, Limited Battery charger
US4686444A (en) * 1984-11-21 1987-08-11 Samsung Electronics Co., Ltd. Battery charging circuit
US4649333A (en) * 1985-04-30 1987-03-10 Levitt-Safety Limited Two terminal nicad battery charger with battery voltage and temperature sensing
US4712055A (en) * 1987-04-01 1987-12-08 The Singer Company Battery charger circuit
US5013993A (en) * 1987-09-04 1991-05-07 Black & Decker Inc. Thermally responsive battery charger
US4890004A (en) * 1988-11-21 1989-12-26 Beckerman Howard L Emergency light control and battery charging system
US5225763A (en) * 1991-03-20 1993-07-06 Sherwood Medical Company Battery charging circuit and method for an ambulatory feeding pump
US5247238A (en) * 1991-04-05 1993-09-21 Yang Tai Her Battery charger automatic cut-off circuit
US5245268A (en) * 1992-04-15 1993-09-14 Jason Wang Battery charger with current stabilizer
US5708350A (en) * 1996-08-09 1998-01-13 Eveready Battery Company, Inc. Recharging method and temperature-responsive overcharge protection circuit for a rechargeable battery pack having two terminals
US6243276B1 (en) 1999-05-07 2001-06-05 S-B Power Tool Company Power supply system for battery operated devices

Also Published As

Publication number Publication date
AU4513179A (en) 1979-10-04
CA1128989A (en) 1982-08-03
NL7901821A (nl) 1979-10-02
GB2018061A (en) 1979-10-10
SE7902748L (sv) 1979-09-30
AU521571B2 (en) 1982-04-08
BE875165A (fr) 1979-07-16
SE432328B (sv) 1984-03-26
GB2018061B (en) 1982-08-04
JPS54139033A (en) 1979-10-29
DE2912509A1 (de) 1979-10-11
IT7948464A0 (it) 1979-03-23
IT1115071B (it) 1986-02-03

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Legal Events

Date Code Title Description
AS Assignment

Owner name: S-B POWER TOOL COMPANY, ILLINOIS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SKIL CORPORATION;REEL/FRAME:006495/0992

Effective date: 19920924